Nanosilver/DCOIT-containing surface coating effectively and constantly reduces microbial load in emergency room surfaces

BACKGROUND

Colonization of near-patient surfaces in hospitals plays an important role as a source of healthcare-associated infections. Routine disinfection methods only result in short-term elimination of pathogens.

AIM

To investigate the efficiency of a newly developed antimicrobial coating containing nanosilver in long-term reduction of bacterial burden in hospital surfaces to close the gap between routine disinfection cycles.

METHODS

In this prospective, double-blinded trial, frequently touched surfaces of a routinely used treatment room in an emergency unit of a level-I hospital were treated with a surface coating (nanosilver/DCOIT-coated surface, NCS) containing nanosilver particles and another organic biocidal agent (4,5-dichloro-2-octyl-4-isothiazolin-3-one, DCOIT), whereas surfaces of another room were treated with a coating missing both the nanosilver- and DCOIT-containing ingredient and served as control. Bacterial contamination of the surfaces was examined using contact plates and liquid-based swabs daily for a total trial duration of 90 days. After incubation, total microbial counts and species were assessed.

FINDINGS

In a total of 2880 antimicrobial samples, a significant reduction of the overall bacterial load was observed in the NCS room (median: 0.31 cfu/cm²; interquartile range: 0.00-1.13) compared with the control coated surfaces (0.69 cfu/cm²; 0.06-2.00; P < 0.001). The nanosilver- and DCOIT-containing surface coating reduced the relative risk of a critical bacterial load (defined as >5 cfu/cm²) by 60% (odds ratio 0.38, P < 0.001). No significant difference in species distribution was detected between NCS and control group.

CONCLUSION

Nanosilver-/DCOIT-containing surface coating has shown efficiency for sustainable reduction of bacterial load of frequently touched surfaces in a clinical setting.

Titanium industrial residues surface modification towards its reuse as antimicrobial surfaces

In this study, a new material obtained from titanium ingots residue was coated with natural carotenoids having antibacterial properties. The waste is a no recycling titanium scrap from technological production process which was pressed and transformed into disks titanium samples. Through anodization and annealing procedures of the titanium disk, a nanostructured titanium dioxide surface with photocatalytic and antibacterial properties was successfully obtained. The titanium scrap impurities (V, Al, and N), unwanted for production process, have shown to improve electrochemical and semiconductor properties of the residue surfaces. The nanostructured titanium scrap surface was modified with two different carotenoids, torularhodin and β-carotene, to potentiate the antibacterial properties. The bactericidal tests were performed against Salmonella typhimurium and Escherichia coli, both Gram-negative. The best bactericidal effect is obtained for nanostructured titanium scrap disks immersed in torularhodin, with a percentage of growth inhibition around 60% against both tested bacteria. The results suggest that this low-cost waste material is suitable for efficient reuse as antibacterial surface after a few simple and inexpensive treatments.

Effective and biocompatible antibacterial surfaces via facile synthesis and surface modification of peptide polymers

It is an urgent need to tackle drug-resistance microbial infections that are associated with implantable biomedical devices. Host defense peptide-mimicking polymers have been actively explored in recent years to fight against drug-resistant microbes. Our recent report on lithium hexamethyldisilazide-initiated superfast polymerization on amino acid N-carboxyanhydrides enables the quick synthesis of host defense peptide-mimicking peptide polymers. Here we reported a facile and cost-effective thermoplastic polyurethane (TPU) surface modification of peptide polymer (DLL: BLG = 90 : 10) using plasma surface activation and substitution reaction between thiol and bromide groups. The peptide polymer-modified TPU surfaces exhibited board-spectrum antibacterial property as well as effective contact-killing ability in vitro. Furthermore, the peptide polymer-modified TPU surfaces showed excellent biocompatibility, displaying no hemolysis and cytotoxicity. In vivo study using methicillin-resistant Staphylococcus aureus (MRSA) for subcutaneous implantation infectious model showed that peptide polymer-modified TPU surfaces revealed obvious suppression of infection and great histocompatibility, compared to bare TPU surfaces. We further explored the antimicrobial mechanism of the peptide polymer-modified TPU surfaces, which revealed a surface contact-killing mechanism by disrupting the bacterial membrane. These results demonstrated great potential of the peptide-modified TPU surfaces for practical application to combat bacterial infections that are associated with implantable materials and devices.

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A convenient surface modification of peptide polymer 90 : 10 DLL : BLG to enable material surfaces antibacterial properties.

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The modified thermoplastic polyurethane (TPU) surfaces show board-spectrum antibacterial performance and excellent biocompatibility both in vitro and in vivo.

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The contact-killing surfaces demonstrate great potential for practical application to combat bacterial infections associated with implantable materials and devices.

Carboxylic acid mediated antimicrobial activity of silicone elastomers

Due to their high biocompatibility silicone elastomers are the material of choice in many sensitive health care applications. However, the inherent hydrophobicity of the polymer makes silicones more susceptible to spontaneous protein adsorption and subsequent biofilm formation than more hydrophilic abiotic materials. Hence, the development of antimicrobial silicone elastomers could help to reduce potential biofilm-associated infections when using silicone based medical devices. In this study, we describe carboxylic-acid-modified silicone elastomers that are biocompatible and exhibit a specific antimicrobial activity against clinically relevant pathogens even after being stored in common packaging materials.

Novel photodynamic coating reduces the bioburden on near-patient surfaces thereby reducing the risk for onward pathogen transmission: a field study in two hospitals

BACKGROUND

Near-patient surfaces are recognized as a source for hospital-acquired infections. Such surfaces act as reservoirs for microbial contamination by which pathogens can be transmitted from colonized or infected patients to susceptible patients. Routine disinfection of surfaces only results in a temporal elimination of pathogens, and recontamination inevitably occurs shortly between disinfections.

AIM

A novel antimicrobial coating based on photodynamics was tested under laboratory conditions and subsequently in a field study in two hospitals under real-life conditions.

METHODS

Identical surfaces received a photodynamic or control coating. Bacterial counts [colony-forming units (cfu)/cm²) were assessed regularly for up to 6 months.

FINDINGS

The laboratory study revealed a mean reduction of several human pathogens of up to 4.0 ± 0.3 log₁₀. The field study in near-patient environments demonstrated mean bacterial values of 6.1 ± 24.7 cfu/cm² on all control coatings. Photodynamic coatings showed a significantly lower mean value of 1.9 ± 2.8 cfu/cm² (P<0.001). When considering benchmarks of 2.5 cfu/cm² or 5 cfu/cm², the relative risk for high bacterial counts on surfaces was reduced by 48% (odds ratio 0.38, P<0.001) or 67% (odds ratio 0.27, P<0.001), respectively.

CONCLUSION

Photodynamic coatings provide a significant and lasting reduction of bacterial counts on near-patient surfaces, particularly for high bacterial loads, in addition to routine hygiene. The promising results of this proof-of-concept study highlight the need for further studies to determine how this novel technology is correlated with the frequency of hospital-acquired infections.

From the Titanic and other shipwrecks to biofilm prevention: The interesting role of polyphenol-protein complexes in biofilm inhibition

Bacteria attach themselves either reversibly or irreversibly onto practically any surface in aqueous and other environments in order to reproduce, while generating extracellular polymeric substances (EPS) as a supportive structure for biofilm formation. Surfaces with a potential to prevent cellular attachment and aggregation (biofilm) would be extremely useful in environmental, biotechnological, medical and industrial applications. The scientific community is currently focusing on the design of micro- and nano-scale textured surfaces with antibacterial and/or antifouling properties (e.g., filtration membranes). Several serum and tissue proteins promote bacterial adhesion (for example, albumin, fibronectin and fibrinogen), whereas polyphenols form complexes with proteins which change their structural, functional and nutritional properties. For example, tannic acid, a compound composed of polygalloyl glucoses or polygalloyl quinic acid esters and several galloyl moieties, inhibits the growth of many bacterial strains. The present review is based on different nautical archaeology research data, and asks a simple but as yet unanswered question: What is the chemistry that prevents leather biodegradation by environmental bacteria and/or formation of biofilms? Future research should answer these questions, which are highly important for biofilm prevention.

Antimicrobial activity of T4 bacteriophage conjugated indium tin oxide surfaces

We report the antimicrobial activity of bare and surface functionalized indium tin oxide (ITO) conjugated with T4 bacteriophage towards E. coli. A ∼ 10³-fold reduction (99.9%) in the bacterial concentration was achieved within 2 h exposure of E. coli to the bare as well as the amine, carboxylic and methyl functionalized ITO/T4 surfaces. Despite the known differences in bacteriophage loading of these ITO/T4 systems, the almost identical extent of antimicrobial activity of all of the ITO/T4 systems resulted from the release of a comparable amount of infective T4 from the systems. As anticipated, a single dose of immobilized bacteriophage was sufficient to eliminate further surge of bacterial population. Upon the 2 h eradication of the '1st batch' of E. coli population, all of the ITO/T4 systems, each system with 10²-fold more suspended bacteriophage (due to propagation of the phage at the expense of the '1st batch' E. coli death), reduced the '2nd batch' of E. coli concentration by ∼10⁴-fold in just 30 min, suggesting the potential of immobilized bacteriophage systems as solution to the issues of antimicrobial agent depletion. All of the ITO/T4 systems maintained their antimicrobial activity in the presence of model food components. The antimicrobial activity was however, affected by pH; at pH 5 whereby the bacteria's growth was physiologically inhibited, generally no reduction in E. coli concentration was detected. The present work provides an understanding of the mode of antimicrobial activity exhibited by an immobilized bacteriophage based substrate and demonstrates efficacy in the presence of food components.

The importance of fungal pathogens and antifungal coatings in medical device infections

In recent years, increasing evidence has been collated on the contributions of fungal species, particularly Candida, to medical device infections. Fungal species can form biofilms by themselves or by participating in polymicrobial biofilms with bacteria. Thus, there is a clear need for effective preventative measures, such as thin coatings that can be applied onto medical devices to stop the attachment, proliferation, and formation of device-associated biofilms. However, fungi being eukaryotes, the challenge is greater than for bacterial infections because antifungal agents are often toxic towards eukaryotic host cells. Whilst there is extensive literature on antibacterial coatings, a far lesser body of literature exists on surfaces or coatings that prevent attachment and biofilm formation on medical devices by fungal pathogens. Here we review strategies for the design and fabrication of medical devices with antifungal surfaces. We also survey the microbiology literature on fundamental mechanisms by which fungi attach and spread on natural and synthetic surfaces. Research in this field requires close collaboration between biomaterials scientists, microbiologists and clinicians; we consider progress in the molecular understanding of fungal recognition of, and attachment to, suitable surfaces, and of ensuing metabolic changes, to be essential for designing rational approaches towards effective antifungal coatings, rather than empirical trial of coatings.

Antimicrobial and antibiofilm efficacy of self-cleaning surfaces functionalized by TiO2 photocatalytic nanoparticles against Staphylococcus aureus and Pseudomonas putida

A photocatalytic sol of TiO₂ nanoparticles has been used for creating self-cleaning antimicrobial flat and porous glass surfaces. The substrates were irradiated to study their photocatalytic properties and behavior in the presence of biofilm-forming bacteria. Smooth glass surfaces and glass microfiber filters were covered with 1.98×10^-3±1.5×10^-4gcm^-2 and 8.55×10^-3±3.0×10^-4gcm^-2 densities, respectively. Self-cleaning properties were analyzed using the methylene blue 365nm UV-A photodegradation test. TiO₂-coated filters achieved rapid and complete photodegradation of methylene blue because of the better TiO₂ dispersion with respect to the glass slides. The effect of functionalized surfaces on the growth and viability of bacteria was studied using the strains Staphylococcus aureus and Pseudomonas putida. After irradiation (2h, 11.2Wm^-2, 290-400nm), the initially hydrophobic surface turned hydrophilic. The antibacterial effect led to extensive membrane damage and significant production of intracellular reactive oxygen species in all TiO₂-loaded irradiated specimens. The reduction of cell viability was over 99.9% (>3-log) for TiO₂ on glass surfaces. However, the polymeric extracellular matrix formed before the irradiation treatment was not removed. This study highlights the importance of bacterial colonization during dark periods and the difficulty of removing the structure of biofilms.

Cells capture and antimicrobial effect of hydrophobically modified chitosan coating on Escherichia coli

Hydrophobically modified chitosan (HMCS), prepared by reacting alkyl aldehyde with chitosan was demonstrated to be an effective antimicrobial and transparent coating. The grafted alkyl chains exist as protruded hydrophobic tails on the HMCS coating surface. In contact with E. coli cells, HMCS coating captured and immobilized the cells via these hydrophobic tails. The hydrophobic tails could also kill the cells captured on the coating surface as visualized by fluorescence microscope. More than 50% of the initially loaded cells (2.5×10⁴ CFU) could be killed after 2h contact with HMCS coating. The cells capture and killing effects of the coating surface could be completely neutralized by treating with α-cyclodextrin to sequester the protruded hydrophobic tails. The facile coating of antimicrobial HMCS on surface also enabled the easy fabrication of patterned E. coli cells arrays.

Quaternary ammonium polyethylenimine nanoparticles for treating bacterial contaminated water

This study highlights the potential application of antimicrobial quaternary ammonium nanomaterials for water disinfection. Quaternary ammonium polyethylenimine (QA-PEI) nanoparticles (NPs) were synthesized by polyethylenimine crosslinking and alkylation with octyl iodide followed by methyl iodide quaternization. Particles modified with octyldodecyl alkyl chains were also prepared and evaluated. The antimicrobial activity of QA-PEI NPs was studied after anchoring in non-leaching polymeric coatings and also in aqueous suspension. Particles at different loadings (w/w) were embedded in polyethylene vinyl acetate and polyethylene methacrylic acid coatings and tested for antimicrobial activity against four representative strains of bacteria in static and dynamic modes. Coatings embedded with fluorescent labelled particles tracked by Axioscope fluorescence microscope during the antimicrobial test indicates no particles leaching out. Coatings loaded with 5% w/w QA-PEI exhibited strong antibacterial activity. Aqueous suspension was tested and found effective for bacterial decontamination at 0.1 ppm and maintains its activity for several weeks.

Antimicrobial properties of a nanostructured eggshell from a compost-nesting bird

Infection is an important source of mortality for avian embryos but parental behaviors and eggs themselves can provide a network of antimicrobial defenses. Mound builders (Aves: Megapodiidae) are unique among birds in that they produce heat for developing embryos not by sitting on eggs but by burying them in carefully tended mounds of soil and microbially decomposing vegetation. The low infection rate of eggs of one species in particular, the Australian brush-turkey (Alectura lathami), suggests that they possess strong defensive mechanisms. To identify some of these mechanisms, we first quantified antimicrobial albumen proteins and characterized eggshell structure, finding that albumen was not unusually antimicrobial, but that eggshell cuticle was composed of nanometer-sized calcite spheres. Experimental tests revealed that these modified eggshells were significantly more hydrophobic and better at preventing bacterial attachment and penetration into the egg contents than chicken eggs. Our results suggest that these mechanisms may contribute to the antimicrobial defense system of these eggs, and may provide inspiration for new biomimetic anti-fouling surfaces.